1. Field of the Invention
This invention relates to a benzophenone compound suitable for use as a photosensitizer.
2. Description of the Related Art
Benzophenone derivatives are commonly used as a photosensitizer or a photoinitiator for facilitating curing of an ultraviolet (UV) curable resin or ink. However, when a conventional benzophenone derivative with small molecular weight is used with a UV curable ink for preparation of a package for foodstuffs, the problems of relatively strong bad odor for the package and migration of the benzophenone derivative from the cured polymer to a surface of the package are likely to occur.
In order to overcome the abovementioned problems, many researches have focused on the preparation of a photosensitizer (or a photoinitiator) having high molecular weights, for example, a polymeric photosensitizer (or photoinitiator).
JP S57-109804 (A) discloses a UV curable composition which is used as a polymeric initiator and is represented by the following formula:

wherein R0 is a C3-10 alkenyl group or a phenyl group substituted with one or two C3-10 alkenyl groups. However, in this patent, the problems of bad odor and migration of the benzophenone compound still occur.
WO 96/33156 discloses a benzophenone compound represented by the following formula:

wherein each of Z and Y1 independently represents an alkylene polyol moiety or a polyalkylene polyol moiety; each of Y2 and Y3 is a univalent group; b ranges from 1 to 5; c ranges from 0 to 4; and p ranges from 0 to 5. When the benzophenone compound of this WO patent is used in a UV curable ink, a relatively large amount of the benzophenone compound and a relatively long time for curing are required. In addition, bad odor is still a problem for the WO patent.